In the continuing war against obesity several derivatives of citric acid, which have been implicated in fatty acid synthesis (see, for example, A. C. Sullivan et al., Lipids, 9, 121 [1974]), have been prepared with the hope of developing a medicinal agent effective against the disease and devoid of undesirable side effects.
Hydroxycitric acids reduce food intake and body weight gain by suppressing appetite and inhibiting fatty acid synthesis (A. C. Sullivan et al., Am. J. Clin. Nutr., 30, 767 [1977]). Aminocitric acids are useful in the treatment of obesity by inhibiting lipogenesis (R. W. Guthrie and R. W. Kierstead, U.S. Pat. No. 3,960,933 [issued June 1, 1976]), as are the ester and amide derivatives of hydroxycitric acid .alpha.-lactone (R. W. Guthrie and R. W. Kierstead, U.S. Pat. No. 3,993,668 [issued Nov. 23, 1976]).
Of the halocitric acids, the fluoro compounds, potent inhibitors of aconitate hydratase, have been found to be too toxic to be useful in the control of obesity (R. J. Dummell and E. Kun, J. Biol. Chem., 244, 2966 (1969)).
Chlorocitric acids have been reported in the scientific and patent literature. D. Pawolleck in Ann., 178, 150 (1875) stated his intention to prepare "monochlorocitric acid" at page 152 and claimed the formation of a "chlorine containing acid" by the addition of hypochlorous acid to aconitic acid at page 156. By application of Pawolleck's method, C. Martius and R. Mave, Z. Physiol. Chem., 269, 23 (1941) claimed that only chlorine-free products were obtained. Recently, C. L. Mehltretter, in U.S. Pat. No. 3,536,630 (issued Oct. 27, 1970) reported that substitution of chlorine for hypochlorous acid in Pawolleck's procedure affords a solution of "disodiumchlorohydroxytricarballylate" in water. Biological properties of the alleged chlorocitric acids were not disclosed. It has now been found that repetition of the prior methods for the addition of hypochlorous acid or chlorine to aconitic acid give only non-chlorine containing products.
Iodo- and bromocitric acids have not been described.